1. Field of the Invention
The present invention relates to an electronic apparatus including a touch panel.
2. Description of the Related Art
An electronic apparatus such as a smartphone and a tablet, in which a touch panel is mounted, has come into wide use. The electronic apparatus may include an electrostatic capacitive touch panel. The electrostatic capacitive touch panel can receive “touch operation” performed by directly bringing a finger of a bare hand into contact with a surface of the touch panel and “hover operation” performed by causing a finger to be positioned at a predetermined height from the surface of the touch panel, without bringing the finger of the bare hand onto contact with the surface of the touch panel. Accordingly, a user can perform an operation with a finger covered with gloves in addition to a bare hand.
FIG. 20 is a diagram illustrating a basic configuration of an electrostatic capacitive touch panel. In FIG. 20, a transmission electrode 101 and a reception electrode 102 are disposed on a lower surface of a dielectric plate 100 at a distance from each other and a driving pulse is applied to the transmission electrode 101 from a driving buffer 103. An electric field is generated when the driving pulse is applied. When a finger or the like enters into the electric field, the number of lines of electric force between the transmission electrode 101 and the reception electrode 102 is reduced and a variation in the number of lines of electric force appears as a variation in the charge in the reception electrode 102. A finger approaching a touch panel is detected from a variation in the charge in the reception electrode 102. An actual touch panel has a plurality of transmission electrodes 101 and a plurality of reception electrodes 102 and detects an instructing object planarly.
FIG. 21 is a diagram illustrating a detection state of a finger when the finger approaches the touch panel gradually. In FIG. 21, FIG. 21(a) illustrates a state when a finger is out of an electric field, FIG. 21(b) illustrates a finger hovering detection state when a finger is in an electric field, and FIG. 21(c) illustrates a finger touch detection state when a finger is completely in an electric field and is brought onto contact with a touch panel.
Examples of a touch panel of a type of receiving “touch operation” are disclosed in Japanese Patent Unexamined Publication No. 2009-087311 and Japanese Patent Unexamined Publication No. 2006-323457.
In an electrostatic capacitive touch panel, a two-dimensional coordinate obtained when water or the like is attached to a surface of the panel is caused to be effective in some cases. This problem can be avoided by detecting the strength of pressure on the touch panel and not detecting pressure occurring due to attachment of water or the like. For example, strain when water or the like is attached is detected by using a strain sensor and a two-dimensional coordinate when a detected strain quantity is equal to or less than a predetermined threshold value is not caused to be effective.
However, when a two-dimensional coordinate obtained by attachment of water or the like being caused to be effective is prevented by using a strain sensor, if an interval (sampling interval) for obtaining a two-dimensional coordinate from the touch panel is longer than a variation time of a strain quantity detected by the strain sensor, it may be difficult to accurately obtain variation in the strain quantity. FIG. 22 is a diagram illustrating an example when a sampling interval Ta for a two-dimensional coordinate is longer than a variation time of a strain quantity. As illustrated in FIG. 22, the maximum value Dvmax of a strain quantity Dv obtained through the touch operation is within the sampling interval Ta of a two-dimensional coordinate and any one of strain quantities Dv1, Dv2, and Dv3 at obtaining timings t1, t2, and t3 of the two-dimensional coordinate is below the strain quantity threshold value TH. Accordingly, the two-dimensional coordinate obtained through the touch operation at this time is not caused to be effective. As in this example, if variation in strain quantity may be accurately obtained, a two-dimensional coordinate obtained through the touch operation is not caused to be effective though there is a touch operation. If being original, it is necessary that a two-dimensional coordinate obtained through a touch operation after the strain quantity Dv exceeds the strain quantity threshold value TH is effective. If there is attachment of water or the like, a two-dimensional coordinate obtained by this may or may be not caused to be effective. However, if there is a touch operation performed by an instructing object such as a finger, it is necessary that a two-dimensional coordinate obtained by this is effective.
Considering these circumstances, an object of the present invention is to provide an electronic apparatus in which when a sampling interval for obtaining a two-dimensional coordinate from a touch panel is longer than a variation time of strain quantity detected by a strain sensor, it is also possible to accurately obtain variation in the strain quantity and it is possible to reliably cause a two-dimensional coordinate obtained by an operation of an instructing object such as a finger to be effective.